How does coffee and caffeine alter risk of breast cancer and ovarian cancer
Early observations of caffeine–cancer association.
Coffee and tea as a source of antioxidants
In 70' and 80' caffeine was supposed to be carcinogenic, i.e. causing cancer. On the other hand there is relatively large amount of natural phenolic compounds in caffeinated beverages (mainly coffee and tea) which acts as antioxidants. They prevent tumor cells growth in mammals through few simultaneous mechanisms and pathways. Green tea, which is particularly rich source of one of phenolic compounds groups called catechins, is believed to prevent breast cancer and prostate cancer specifically. Interestingly in 2006 United States Food and Drug Administration approved an ointment based on green tea and added it to the Prescription Drug Product List for warts topical treatment. However, FDA concludes that:
…there is very limited credible evidence for qualified health claims specifically for green tea and breast cancer and for green tea and prostate cancer.[1]
It's clear that some evidences seems to be contradictory and scientific research is needed to reveal the truth.
Caffeine abuse and breast cancer
Group of researchers from Harvard School of Public Health, Boston, MA, made an attempt to investigate the relation between caffeine intake and breast cancer risk. The study is based on large number of participants – during 22 years (from 1980 to 2002) nearly 86 thousand of women have taken a part in evaluation of the caffeine-cancer relation. Over 5 thousands of them have suffered from breast cancer during this period of time. The results seems to be quite optimistic. However, as researchers underline (in their article published in 2008 in International Journal of Cancer) many questions remain unsettled.
We observed no substantial association between caffeinated and decaffeinated coffee and tea consumption and risk of breast cancer in the overall cohort. However, our results suggested a weak inverse association between caffeine-containing beverages and risk of postmenopausal breast cancer.[2]
Researchers led by D. Ganmaa haven't found significant association between caffeine consumption and breast cancer incidents. But they have observed a weak overall inverse association with caffeine intake, and this association was stronger in postmenopausal women compared to premenopausal women
. It means and suggest that coffee consumption reduces the risk of breast cancer in postmenopausal women (as they say: especially receptor positive type of cancer).
Authors pay our attention to research published in 1985 where breast cancer risk in rats was examined in relation to caffeine intake and its dosage. Caffeine decreased incidents of hormone-induced rat breast cancer – the higher caffeine dosage the smaller number of animals with cancers and longer time to develop first cancer in a given organism. Additionally caffeine breast cancer-preventing effects was reported for example by Hunter in 1992 and Michels in 2002, while Norwegian researchers led by Vatten et al. suggested in 1990 that preventing effects take place among lean women, whereas among obese women higher doses of caffeine ingested every day increases the risk of breast cancer. Ganmaa et all concludes:
Higher consumption of caffeine-containing beverages may modestly reduce risk of postmenopausal breast cancer, and this relation needs to be examined further.[2]
Caffeine abuse and ovarian cancer
American-Australian research group led by Tworoger gave the similar ideas according to their investigations on caffeine / alcohol / tobacco smoking, and the risk of incident epithelial ovarian cancer. Results were reported recently in article published in 'Cancer' in March 2008[3]. Over 80 thousands women were examined from 1976 to 2004.
Researchers also observed an inverse association of ovarian cancer risk with caffeine use what means that caffeine acts as a ovarian cancer preventing agent with 20% risk decrease. Effects was stronger in postmenopausal women but only among those who had never used postmenopausal hormones (PMH). Positive effecs was also observed among women who do not use oral contraceptives. However, results were not statistically significant and authors say that it should be interpreted with caution. They summarize:
Caffeine was suggestively, inversely associated with postmenopausal ovarian cancer (…), but was positively associated with premenopausal ovarian cancer (…). However, this interaction was not statistically significant, likely because of the limited number of premenopausal cases.[3]
Authors indicate that their results are in accordance with other reported before. For example research reported in article 'Coffee, tea and caffeine and risk of epithelial ovarian cancer'[4] published in 2004, also found caffeine to be inversely associated with ovarian cancer risk. Association was stronger in postmenopausal women (which is in accordance with works on breast cancer). However, some other results are contradictory: two studies among premenopausal women report positive association for caffeine and few investigations haven't found any association between caffeine intake and ovarian cancer risk.
Alcohol and tobacco smoking were also under consideration in Tworoger's study reported here, but there was no association between ovarian cancer risk and alcohol or tobacco use. However, we have to remember that smoking is strongly associated with mucinous tumors, to what authors pay our attention.
References
[1] US FDA/CFSAN - Letter Responding to Health Claim Petition dated January 27, 2004: Green Tea and Reduced Risk of Cancer Health Claim (Docket number 2004Q-0083)
[2] Ganmaa D, Willett WC, Li TY, Feskanich D, van Dam RM, Lopez-Garcia E, Hunter DJ, Holmes MD; Coffee, tea, caffeine and risk of breast cancer: A 22-year follow-up, International Journal of Cancer, 2008, 122, 2071
[3] Tworoger SS, Gertig DM, Gates MA, Hecht JL, Hankinson SE; Caffeine, Alcohol, Smoking, and the Risk of Incident Epithelial Ovarian Cancer, Cancer, 2008, 112, 1169
[4] Jordan SJ, Purdie DM, Green AC, Webb PM., Coffee, tea and caffeine and risk of epithelial ovarian cancer, Cancer Causes & Control, 2004, 15, 359.
